A wide variety of medical isotopes find use in medical imaging and/or therapeutic applications. There is a continuing need for the development of improved technologies for utilizing such agents. There is a particular need for the development of technologies that facilitate effective use of radio- or therapeutic medical isotopes, for example, radiolabeled nanoparticles.
Traditional approaches to nanoparticle radiolabeling have typically been customized for particular radioisotopes and have achieved radiolabeling of nanoparticles via surface functionalization of small molecular chelating agents that bind specific radioisotopes. Such traditional approaches enable utilization of labeling protocols that have already been established in molecular chelator research, but present several disadvantages. Since the coordination chemistry of different isotopes varies greatly, there is no molecular chelator that can effectively bind many radioisotopes interchangeably. Thus, for a given radiotracer, selection of and particle modification with the proper chelator may be very difficult or even impossible. Even when isotopes are stably chelated during radiolabeling, introduction of the nanoparticle in vivo presents a new set of challenges. Transchelation by endogenous proteins or detachment of the surface-bound molecular chelators can strip the nanoparticles of their radiolabels, yielding images that do not reflect the true biodistribution. Traditional approaches, among other problems, remain restricted to specific isotopes, rather than being general platforms for many species.